The Home Office is to "evaluate the impact" of the 24-hour licensing laws brought in at the end of 2005.

The prime minister's official spokesman said it is due to report back at the end of the year, with the evaluation due to run until the autumn.

PM Gordon Brown said that only a small fraction of pubs had embraced 24-hour drinking and it had not caused any significant increase in arrests.

His spokesman said the government would look at the law in "a sober way".

Speaking to journalists, the spokesman said Mr Brown would not be "widening" the remit of the Home Office review, but said he wanted to "examine in an objective way the evidence".

Puritan tendencies

Earlier, during his press conference, Mr Brown had been asked if he would reverse the policy on 24-hour drinking, in a similar fashion to government moves to re-examine the supercasino decision and cannabis classification.

Mr Brown said they had been "very specific issues".

Questioned if the 24-hour culture was at odds with a perceived Puritan streak, Mr Brown joked: "I came to London in 1983, I have been in London for more than 20 years."

He recalled a Mark Twain joke about having arrived in Nevada, with its gambling, drinking and womanising, from a Puritan background.

Mr Brown quoted the American author as saying: "This was no place for a Puritan and I did not long remain one."